This Research Note examines the potential for tools based on gathering and analysis of audio data to enhance the capabilities of cities that aspire to be smarter. Audio-based monitoring and surveillance, and other audio applications in urban contexts such as noise mapping, are likely to become increasingly interesting to cities. There is a wide variety of tools with different purposes and in different stages of development, from science projects in ‘Living Lab’ deployments to mature commercial products aimed at helping city departments to deliver on specific goals.